The invention relates to a metal-infiltrated polycrystalline diamond composite tool. More particularly, the invention relates to diamond particles that are used to form such a tool. Even more particularly, the invention relates to diamond particles having an activated surface layer. Finally, the invention relates to a method of forming a metal-infiltrated polycrystalline diamond composite tool from diamond particles having such an activated surface layer.
Polycrystalline diamond tools are often manufactured from dense blanks that are formed by infiltrating a matrix of diamond particles with a molten metal, such as cobalt. The molten metal acts as a liquid-state sintering aid, partially dissolving the diamonds and producing diamond-to-diamond bonding within the composite. One problem encountered with infiltrating the bed of diamond particles is that the metal does not wet the surface of the diamonds well. As a result, the matrix is not completely infiltrated and the diamond-to-diamond bonds are not formed in some locations, thus preventing the optimization of the overall strength and abrasion resistance of the cutting tool.
To improve wetting of the diamonds by the molten metal, the diamonds in such tools may be initially coated with the samexe2x80x94or similarxe2x80x94metal that is used as an infiltrant metal to facilitate infiltration and formation of the diamond-to-diamond bonds. An electroless plating technique, in which the diamonds are exposed to a solution containing the coating material, has been used to coat diamond particles with a metal. Electroless plating of a substrate, however, requires a catalytic reduction of metal ions in the presence of a reducing agent. For non-conducting materials such as diamond, the substrate surface must therefore be activated prior to plating. In contrast, many metal substrates do not require such activation, as the surface is already catalytic.
Palladium (Pd) is frequently used to activate substrate materials prior to coating. The most common procedure is to first sensitize the substrate surface with tin dichloride (SnCl2), followed by activation using a solution of Pd and hydrochloric acid (HCl). Alternatively, a colloidal Pd solution, which also frequently contains Sn, can be used to activate the substrate surface. One of these two methods is commonly used in the electroless plating of diamond. Kanada et al. (U.S. Pat. No. 5,759,216), for example, have used an activation solution comprised substantially of palladium to obtain metal-coated diamonds, which were subsequently used to form polycrystalline diamond (PCD) under high pressure and high temperature conditions.
One drawback to the use of palladium as an activating metal is its expense. It is therefore desirable to identify a less expensive alternative procedure for producing metallic coatings that are applied to the diamond particles. Therefore, what is needed is a diamond particle having a palladium-free coating that enhances wetting by the molten metal infiltrant. What is also needed is a diamond particle coated with an activation layer formed from a relatively inexpensive metal, the activation layer being capable of catalytically reducing metallic coatings that are applied to the diamond particles by electroless deposition. What is further needed is a method of applying such an activation layer to the diamond particles. In addition, what is needed is a metal-infiltrated polycrystalline diamond composite tool that comprises a number of diamond particles having;,such an activation layer. Finally, what is needed is a method of forming such a tool.
The present invention satisfies these needs and others by providing a metal-infiltrated polycrystalline diamond composite tool having a plurality of diamond grains forming a continuous polycrystalline diamond matrix, the polycrystalline diamond matrix being interpenetrated by a substantially palladium-free metallic phase. The present invention also provides a preform for such metal-infiltrated polycrystalline diamond composite tools, in which diamond particles having a substantially palladium-free wetting enhancement layer contact a metallic infiltrant source. The present invention also provides methods of making a metal-infiltrated polycrystalline diamond composite tool, a preform, and a coated diamond particle for such a tool, all of which are substantially palladium-free.
Accordingly, one aspect of the present invention is to provide a metal-infiltrated polycrystalline diamond composite tool. The metal-infiltrated polycrystalline diamond composite tool comprises: a plurality of diamond grains, the plurality of diamond grains forming a continuous polycrystalline diamond matrix;
a substantially palladium-free metallic phase, the metallic phase being substantially palladium-free and contiguous to the continuous polycrystalline diamond matrix, wherein the metallic phase interpenetrates the continuous polycrystalline diamond matrix and substantially wets an outer surface of the continuous polycrystalline diamond matrix; and a working surface.
A second aspect of the invention is to provide a preform for a metal-infiltrated polycrystalline diamond composite tool. The preform comprises: a container formed from a refractory material; a plurality of coated diamond particles disposed in the container and forming a bed therein, each of the plurality of coated diamond particles comprising a diamond having an outer surface and a wetting-enhancement coating disposed thereon, the wetting-enhancement coating being substantially palladium-free and comprising at least one metal selected from the group consisting of cobalt, iron, and nickel, wherein the wetting-enhancement coating substantially covers the outer surface; and a metallic infiltrant source disposed in the container and contacting the bed of the plurality of: coated diamond particles. The metallic infiltrant source comprises at least one metal selected from the group consisting of cobalt, iron, and nickel.
A third aspect of the invention is to provide a metal-infiltrated polycrystalline diamond composite tool formed from a preform. The preform comprises: a container formed from a refractory material; a plurality of coated diamond particles disposed in the container and forming a bed therein, each of the plurality of coated diamond particles comprising a diamond having an outer surface and a wetting-enhancement coating disposed thereon, the wetting-enhancement coating being substantially palladium-free and comprising a metal selected from the group consisting of cobalt, iron, and nickel, wherein the wetting-enhancement coating substantially covers the outer surface; and a metallic infiltrant source contacting the bed of the plurality of coated diamond particles. The metal-infiltrated polycrystalline diamond composite tool comprises: a plurality of diamond grains, the plurality of diamond grains forming a continuous polycrystalline diamond matrix; a metallic phase, the metallic phase being substantially palladium-free and contiguous to the continuous polycrystalline diamond matrix, wherein the metallic phase interpenetrates the continuous polycrystalline diamond: matrix and substantially wets an outer surface of the continuous polycrystalline diamond matrix, and wherein the metallic phase comprises at least one metal selected from the group consisting of cobalt, iron, and nickel; and an abrasive working surface;.
A fourth aspect of the invention is to provide a method of making a metal-infiltrated polycrystalline diamond composite tool. The method comprises the steps of: providing a preform, the preform comprising: a container containing a metallic infiltrant, the metallic infiltrant being substantially palladium-free, and a plurality of coated diamond particles, wherein each of the coated diamond particles comprises a diamond having an outer surface and a substantially palladium-free wetting-enhancement coating disposed thereon; infiltrating the plurality of coated diamond particles with the metallic infiltrant and producing diamond-to-diamond bonding, thereby forming a metal-infiltrated polycrystalline diamond composite blank; and forming a working surface on at least one surface of the metal-infiltrated polycrystalline diamond composite blank, thereby forming the metal-infiltrated polycrystalline diamond composite tool.
A fifth aspect of the invention is to provide a method of making a coated diamond particle for use in a metal-infiltrated polycrystalline diamond composite tool. The method comprises the steps of: providing a diamond; and coating an outer surface of the diamond with a substantially palladium-free wetting-enhancement coating comprising a metal selected form the group consisting of cobalt, iron, and nickel, such that the substantially palladium-free wetting-enhancement coating substantially covers the outer surface, thereby forming a coated diamond particle.
Finally, a sixth aspect of the invention is to provide a method of making a preform for a metal-infiltrated polycrystalline diamond composite tool. The method comprising the steps of: providing a container formed from a refractory material; providing a plurality of coated diamond particles to the container, each of the coated diamond particles comprising a diamond having an outer surface and a substantially palladium-free wetting-enhancement coating disposed thereon; and providing a substantially palladium-free metallic infiltrant source to the container such that the substantially palladium-free metallic infiltrant source contacts the plurality of coated diamond particles.